Electric storage device

ABSTRACT

An electric storage device includes a plurality of storage modules and a first storage-module busbar. The plurality of storage modules each include a storage-cell busbar and a plurality of storage cells. The storage-cell busbar includes a first storage-module terminal at a first end of the storage-cell busbar. The plurality of storage cells are electrically connected to each other with the storage-cell busbar. The first storage-module terminal provided in one of the plurality of storage modules is electrically connected to the first storage-module terminal provided in another of the plurality of storage modules with the first storage-module busbar. The first storage-module terminal includes a first stud bolt which extends through a bolt hole provided in the first storage-module busbar and to which a nut is fastened.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2012-245023, filed Nov. 7, 2012, entitled “Electric Storage Device.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

b 1. Field

The present disclosure relates to an electric storage device.

2. Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2010-272520 describes a storage module including a plurality of storage cells that are stacked together and a pair of end plates stacked on outer surfaces of the stack of storage cells, the storage cells and the end plates being fastened together by stack members. A pair of reinforcing members are stacked on outer surfaces of the pair of end plates of the storage module in the stacking direction, and are fixed to a pair of support plates with pins at the bottom ends thereof.

Electric storage devices including a plurality of storage modules are generally configured such that a plurality of storage cells included in each storage module are electrically connected to each other with a storage-cell busbar and storage-module terminals provided at the ends of the storage-cell busbars are electrically connected to each other with a storage-module busbar.

SUMMARY

According to one aspect of the present invention, an electric storage device includes a plurality of storage modules and a first storage-module busbar. The plurality of storage modules each include a storage-cell busbar and a plurality of storage cells. The storage-cell busbar includes a first storage-module terminal at a first end of the storage-cell busbar. The plurality of storage cells are electrically connected to each other with the storage-cell busbar. The first storage-module terminal provided in one of the plurality of storage modules is electrically connected to the first storage-module terminal provided in another of the plurality of storage modules with the first storage-module busbar. The first storage-module terminal includes a first stud bolt which extends through a bolt hole provided in the first storage-module busbar and to which a nut is fastened.

According to another aspect of the present invention, an electric storage device includes a plurality of storage modules and a first storage-module busbar. The plurality of storage modules each include a storage-cell busbar and a plurality of storage cells. The storage-cell busbar includes a first storage-module terminal at a first end of the storage-cell busbar. The plurality of storage cells are electrically connected to each other with the storage-cell busbar. The plurality of storage modules are arranged next to each other and integrally fastened to a first connection plate with first bolts. The first storage-module terminal provided in one of the plurality of storage modules is electrically connected to the first storage-module terminal provided in another of the plurality of storage modules with the first storage-module busbar. The first storage-module terminal includes a first stud bolt which extends in a direction same as an insertion direction of the first bolts and to which a nut is fastened. The first stud bolt extends through a bolt hole provided in the first storage-module busbar.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

FIG. 1 is a perspective view of a storage module.

FIG. 2 is an exploded perspective view of the storage module.

FIGS. 3A to 3C are diagrams illustrating the relationship between a main plate and a sub-plate in each end plate.

FIG. 4 is an exploded perspective view of an electric storage device.

FIGS. 5A and 5B are diagrams illustrating the structure of FIG. 4 viewed in the direction of arrow VA, VB.

FIGS. 6A and 6B are diagrams illustrating the structure of FIG. 4 viewed in the direction of arrow VIA, VIB.

FIG. 7 is an enlarged view of part VII in FIG. 5A.

FIG. 8 is a sectional view of FIG. 7 taken along line VIII-VIII.

FIG. 9 is a sectional view of FIG. 6B taken along line IX-IX.

FIG. 10 is an enlarged view of part X in FIG. 6B.

FIGS. 11A and 11B are diagrams illustrating the states in which storage modules are electrically connected.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.

The embodiment of the present disclosure will be described with reference to FIGS. 1 to 11B.

Referring to FIGS. 1 and 2, a storage module M, which is used as a power source of an electric vehicle or a hybrid vehicle, includes a predetermined number of storage cells 11 (twelve storage cells 11 in the present embodiment) which are stacked in a stacking direction. Each storage cell 11 has a rectangular parallelepiped shape, and includes a pair of main surfaces 11 a that oppose each other, a pair of side surfaces 11 b that are orthogonal to the main surfaces 11 a and oppose each other, and top and bottom surfaces 11 c and 11 d that are orthogonal to the main surfaces 11 a and the side surfaces 11 b and oppose each other. Positive and negative electrodes 11 e are provided on the top surface 11 c.

In this specification, the direction that is orthogonal to the stacking direction and in which the top and bottom surfaces 11 c and 11 d of each storage cell 11 are arranged is defined as the up-down direction. The direction that is orthogonal to the stacking direction and in which the pair of side surfaces 11 b of each storage cell 11 is arranged is defined as the left-right direction.

The main surfaces 11 a of the twelve storage cells 11 and eleven rectangular plate-shaped intermediate storage cell holders 12, which are made of a synthetic resin, are alternately stacked in the stacking direction. A pair of rectangular plate-shaped end storage cell holders 12A and 12B, which are also made of a synthetic resin, are stacked on the outer surfaces of the two outermost storage cells 11 in the stacking direction, and a pair of end plates 14A and 14B, which are made of a metal, are stacked on the outer surfaces of the end storage cell holders 12A and 12B in the stacking direction. The eleven intermediate storage cell holders 12 have the same shape and are interchangeable. The end storage cell holders 12A and 12B have different shapes, and the shapes thereof also differ from the shape of the intermediate storage cell holders 12.

The storage module M is assembled by stacking the storage cells 11, the intermediate storage cell holders 12, the end storage cell holders 12A and 12B, and the end plates 14A and 14B in the stacking direction and connecting four corners of the end plate 14A to the respective corners of the end plate 14B with a pair of upper restraining bands 15, which are rod-shaped metal members having an L-shaped cross section, and a pair of lower restraining bands 16, which are also rod-shaped metal members having an L-shaped cross section. More specifically, the storage module M is assembled by bringing thick end-plate fixing portions 15 a, which are provided at both ends of the upper restraining bands 15, and thick end-plate fixing portions 16 a, which are provided at both ends of the lower restraining bands 16, into contact with the respective corners of the end plates 14A and 14B and screwing bolts 17 into the end-plate fixing portions 15 a and 16 b through the end plates 14A and 14B.

An upper insulator 18 is disposed between each upper restraining band 15 and the unit including the storage cells 11, the intermediate storage cell holders 12, and the end storage cell holders 12A and 12B. The upper insulators 18 are made of a synthetic resin and serve to prevent liquid junction between the storage cells 11 and the upper restraining bands 15 due to condensate. Similarly, a lower insulator 19 is disposed between each lower restraining band 16 and the unit including the storage cells 11, the intermediate storage cell holders 12, and the end storage cell holders 12A and 12B. The lower insulators 19 are also made of a synthetic resin and serve to prevent liquid junction between the storage cells 11 and the lower restraining bands 16 due to condensate. In addition, leaf springs 20 are disposed between each lower restraining band 16 and the corresponding lower insulator 19 to press the bottom surfaces 11 d of the storage cells 11 upward and prevent rattling.

A U-shaped storage-cell busbar 21 is attached to the top surface of the storage module M. The storage-cell busbar 21 electrically connects the electrodes 11 e of the twelve storage cells 11 in series. Accordingly, among the pair of end plates 14A and 14B, one end plate 14A serves as a high-potential-side (positive side) end plate, and the other end plate 14B serves as a low-potential-side (negative side) end plate. The end plates 14A and 14B have different shapes and are not interchangeable so that, when a plurality of storage modules M are connected in series or parallel, high-potential-side and low-potential-side terminals can be prevented from being assembled incorrectly. Since the cost will increase when two types of end plates 14A and 14B having different shapes are individually manufactured, in the present embodiment, the end plates 14A and 14B having different shapes are formed by combining main plates 22 and sub-plates 23.

As illustrated in FIGS. 3A to 3C, 7, and 8, each main plate 22 has a substantially rectangular shape and includes restraining-band fastening portions 22 a that project outward at four corners thereof, each restraining-band fastening portion 22 a having a bolt hole 22 b formed therein. Each sub-plate 23 has a substantially linear shape and has restraining-band fastening portions 23 a at both ends thereof, each restraining-band fastening portion 23 a having a bolt hole 23 b formed therein. Each main plate 22 and the corresponding sub-plate 23 are welded together at two positions (in fixing regions A).

Each sub-plate 23 includes a pair of fastening portions 30 having respective protruding portions 23 e that have a truncated conical shape and protrude in a direction away from the corresponding main plate 22, respective fastening holes 23 d formed at the centers of the protruding portions 23 e, and respective cut portions 23 f formed by cutting parts of the protruding portions 23 e at the periphery of the protruding portions 23 e. Weld nuts 24 are welded on the back surface of the sub-plate 23 at locations where the fastening holes 23 d are formed at the centers of the protruding portions 23 e of the fastening portions 30. A single jig receiving hole 23 c is formed in a central portion of the sub-plate 23.

Each main plate 22 and the corresponding sub-plate 23 are welded together in the pair of fixing regions A, and are fastened together by the bolts 17 in a pair of fixing regions B in which the bolt holes 22 b and 23 b are formed. The fastening portions 30 are disposed between the fixing regions A and B, and are easily deformable owing to the protruding portions 23 e and the cut portions 23 f.

As is clear from FIGS. 3A to 3C, one end plate 14A is formed by welding one main plate 22 and one sub-plate 23 together in the fixing regions A such that the sub-plate 23 extends along one of the two diagonals of the main plate 22. The other end plate 14B is formed by welding one main plate 22 and one sub-plate 23 together in the fixing regions A such that the sub-plate 23 extends along the other one of the two diagonals of the main plate 22. The end plates 14A and 14B are different members having different shapes that are plane-symmetrical with respect to each other, similar to the shapes of left and right hands. Therefore, when one end plate 14A is configured as a high-potential-side end plate and the other end plate 14B as a low-potential-side end plate, storage modules M can be connected in series or parallel without being incorrectly assembled.

In the state in which the end plates 14A and 14B are assembled by bonding the main plates 22 to the respective sub-plates 23, five pressing points a and b are provided on each main plate 22 (see FIG. 7). A central pressing point a is provided at the center of the jig receiving hole 23 c formed in the sub-plate 23, and four peripheral pressing points b are provided at locations outside the sub-plate 23.

To assemble each storage module M, the twelve storage cells 11 and the eleven intermediate storage cell holders 12 are alternately stacked, and the pair of end storage cell holders 12A and 12B and the pair of end plates 14A and 14B are successively stacked on the stack at both ends of the stack in the stacking direction. In this state, as illustrated in FIGS. 7 and 8, the main plates 22 of the pair of end plates 14A and 14B are pressed toward each other by a pair of jigs, each of which has five pressing pins 25, at the five pressing points a and b. Thus, the storage cells 11, the end storage cell holders 12A and 12B, and the intermediate storage cell holders 12 are compressed. In this state, four bolts 17 are screwed into the end-plate fixing portions 15 a of the upper restraining bands 15 and the end-plate fixing portions 16 a of the lower restraining bands 16 at each end of the storage module M. Thus, the storage module M is assembled.

Among the four bolts 17, two bolts 17 are inserted through only the bolt holes 22 b of the corresponding main plate 22, but the other two bolts 17 are inserted through not only the bolt holes 22 b of the main plate 22 but also the bolt holes 23 b of the corresponding sub-plate 23. Therefore, the strength of each of the end plates 14A and 14B can be increased by fastening the main plate 22 and the sub-plate 23 together with the other two bolts 17. The central pressing point a is pressed by the corresponding pressing pin 25 that is inserted through the jig receiving hole 23 c formed in the sub-plate 23. Therefore, even when there is a gap between the main plate 22 and the sub-plate 23, the pressing point a of the main plate 22 can be efficiently pressed without damaging the sub-plate 23. In addition, the five pressing points a and b can be arranged in a balanced manner and pressed by a uniform pressing force.

As illustrated in FIGS. 4 to 6B, six storage modules M are connected in series to constitute an electric storage device P. The electric storage device P includes first and second connection plates 26A and 26B (connection plate), an upper plate 27, and a lower plate 28. The six storage modules M are arranged next to each other between the first and second connection plates 26A and 26B at an angle of 90° with respect to the up-down direction. Each of the first and second connection plates 26A and 26B includes twelve fastening portions 30 having a truncated conical shape. The end plates 14A and 14B of the six storage modules M are fastened to the first and second connection plates 26A and 26B by inserting bolts 29 through reference fastening holes 26 a formed at the centers of the fastening portions 30 and the fastening holes 23 d formed in the sub-plates 23 and screwing the bolts 29 into the weld nuts 24 on the back surfaces of the sub-plate 23. Then, the electric storage device P is assembled by fastening the upper plate 27 and the lower plate 28 to the first and second connection plates 26A and 26B. In this state, top portions of the fastening portions 30 of the first and second connection plates 26A and 26B are in contact with top portions of the respective fastening portions 30 of the end plates 14A and 14B.

As described above, the bolts 29 used to fix the first and second connection plates 26A and 26B to the six storage modules M are fastened in the stacking direction of the storage cells 11. Therefore, a sufficient distance can be provided between the tool used to fasten the bolts 29 and each of the first and second connection plates 26A and 26B without changing the shape of the first and second connection plates 26A and 26B. As a result, the work efficiency of the fastening process can be increased and the size of the first and second connection plates 26A and 26B can be reduced.

In addition, the end plates 14A and 14B and the first and second connection plates 26A and 26B, which are fastened by the bolts 29, include the fastening portions 30 that are easily deformable by the fastening force applied by the bolts 29. Therefore, even when the storage modules M have different lengths in the stacking direction owing to differences in thickness between the storage cells 11, the fastening portions 30 of the end plates 14A and 14B and the first and second connection plates 26A and 26B can be deformed so as to absorb the differences. Thus, the end plates 14A and 14B and the first and second connection plates 26A and 26B can be prevented from receiving an excessive stress.

Each of the fastening portions 30 of the end plates 14A and 14B is located between two fixing regions A and B in which each sub-plate 23 is fixed to the corresponding main plate 22, and is therefore sufficiently spaced from the fixing regions A and B and easily deformable. Therefore, the differences in dimension in the stacking direction between the storage modules M can be effectively absorbed. In particular, each fastening portion 30 includes the protruding portion 23 e that protrudes from the corresponding sub-plate 23, the fastening hole 23 d that is formed in the protruding portion 23 e and through which the corresponding bolt 29 extends, and the cut portion 23 f formed by cutting a part of the protruding portion 23 e. Therefore, the differences in dimension in the stacking direction between the storage modules M can be more effectively absorbed by causing the protruding portions 23 e having the cut portions 23 f to deform.

The end-plate fixing portions 15 a and 16 a, which are in contact with the outer surfaces of the stack of storage cells 11 in the stacking direction, are respectively provided at the ends of the upper and lower restraining bands 15 and 16, and the end plates 14A and 14B are fixed to the end-plate fixing portions 15 a and 16 a. Therefore, vibration applied to the end plates 14A and 14B through the first and second connection plates 26A and 26B is transmitted to the upper and lower restraining bands 15 and 16 through the end plates 14A and 14B, so that stress concentration does not easily occur in the end plates 14A and 14B. Accordingly, the weight of the end plates 14A and 14B can be reduced by reducing the strength of the end plates 14A and 14B.

The end plates 14A and 14B are formed by stacking the sub-plates 23 onto the main plates 22, and the first and second connection plates 26A and 26B are fastened to the sub-plates 23. Since the sub-plates 23 are fixed to the end-plate fixing portions 15 a and 16 a of the upper and lower restraining bands 15 and 16, vibration applied to the first and second connection plates 26A and 26B can be transmitted to the upper and lower restraining bands 15 and 16 through the sub-plates 23 of the end plates 14A and 14B and the end-plate fixing portions 15 a and 16 a, so that stress concentration does not easily occur in the main plates 22 of the end plates 14A and 14B.

As illustrated in FIGS. 1, 5A, 5B, 6A, and 6B, a pair of storage-module terminals 31A and 31B are provided at respective ends of each storage-cell busbar 21. The storage-module terminals 31A and 31B include respective stud bolts 32 that project outward in the stacking direction. An insulating cover 21 a of each storage-cell busbar 21 has cut portions 21 b in regions around the stud bolts 32. Each cut portion 21 b surrounds three sides of the corresponding stud bolt 32 and is open at one side, and the cut portions 21 b are oriented so that the open sides thereof face different directions. More specifically, in the storage-module terminals 31A, which are exposed at openings 26 b formed in the first connection plate 26A, the open sides of the cut portions 21 b formed around the stud bolts 32 face the outside of the respective storage modules M (see FIGS. 5A and 5B). In the storage-module terminals 31B, which are exposed at openings 26 b formed in the second connection plate 26B, the open sides of the cut portions 21 b formed around the stud bolts 32 face the inside of the respective storage modules M (see FIGS. 6A and 6B).

As illustrated in FIGS. 5A and 5B, four storage-module terminals 31A that are disposed in an inner region of the first connection plate 26A are electrically connected to one another by two short storage-module busbars 33A (storage-module busbar). Each short storage-module busbar 33A has bolt holes 33 a at both ends thereof. The stud bolts 32 of the storage-module terminals 31A of two storage modules M that are adjacent to each other are inserted through the bolt holes 33 a, and nuts 34 are fastened to the stud bolts 32.

As illustrated in FIGS. 6A, 6B, and 10, the six storage-module terminals 31B at the second-connection-plate-26B side are connected to one another by three long storage-module busbars 33B (storage-module busbar). Each long storage-module busbar 33B has bolt holes 33 a at both ends thereof. The stud bolts 32 of the storage-module terminals 31B of two storage modules M that are adjacent to each other are inserted through the bolt holes 33 a, and nuts 34 are fastened to the stud bolts 32.

As described above, the insertion direction of the bolts 29 for fastening the first and second connection plates 26A and 26B to the end plates 14A and 14B is the same as the attachment direction of the nuts 34 for fastening the short storage-module busbars 33A and the long storage-module busbars 33B to the stud bolts 32 of the storage-module terminals 31A and 31B. However, the bolts 29 and the nuts 34 cannot be attached when they are switched. Accordingly, the risk of incorrect assembly due to switching of the bolts 29 and the nuts 34 can be reduced. As a result, the risk that, for example, the first and second connection plates 26A and 26B will be fastened to the end plates 14A and 14B with bolts longer than the bolts 29 that are expected to be used by mistake and the storage cells 11 will be grounded by the longer bolts can be reduced.

In particular, the fastening distance of the stud bolts 32 (the thickness of the short storage-module busbars 33A and the long storage-module busbars 33B) is smaller than the fastening distance of the bolts 29 (the sum of the thickness of the first and second connection plates 26A and 26B and the thickness of the end plates 14A and 14B). Therefore, according to the related art in which short bolts are used instead of the stud bolts 32, there is a risk that grounding will occur as a result of bolts longer than the bolts to be used (in other words, the bolts 29 for fixing the first and second connection plates 26A and 26B) being used by mistake. In contrast, according to the present disclosure, since the stud bolts 32 are used, the risk that switching of the bolts will occur can be eliminated and the above-described problem can be solved.

When the short storage-module busbars 33A and the long storage-module busbars 33B are assembled, the stud bolts 32 extend in a direction that crosses the vertical direction. Therefore, when the stud bolts 32 of the storage-module terminals 31A and 31B are engaged with the bolt holes 33 a formed in the short storage-module busbars 33A and the long storage-module busbars 33B, the nuts 34 can be fastened to the stud bolts 32 while the short storage-module busbars 33A and the long storage-module busbars 33B are provisionally retained and prevented from falling due to gravity.

Among the six storage modules M that are arranged next to each other, the first and second storage modules M from each end in the arrangement direction, for example, are arranged such that the storage-module terminals 31A and 31B thereof face away from each other, and are connected to each other by one of the long storage-module busbars 33B. The second and third storage modules M from each end in the arrangement direction are arranged such that the storage-module terminals 31A and 31B thereof face each other, and are connected to each other by one of the short storage-module busbars 33A. Therefore, the long storage-module busbars 33B and the short storage-module busbars 33A, which have different lengths, cannot be switched and incorrectly assembled by mistake and incorrect assembly can thus be prevented. In addition, even when the number of storage modules M is increased, the short storage-module busbars 33A and the long storage-module busbars 33B may be used for all of the storage modules M. Therefore, the cost can be reduced.

The storage-module terminals 31A and 31B are covered with the insulating covers 21 a, and the cut portions 21 b of the covers 21 a that cover the storage-module terminals 31B, to which the long storage-module busbars 33B are connected, and the cut portions 21 b of the covers 21 a that cover the storage-module terminals 31A, to which the short storage-module busbars 33A are connected, are oriented in different directions (see FIGS. 5A, 5B, 6A, and 6B). Therefore, even when the long storage-module busbars 33B and the short storage-module busbars 33A are switched by mistake, they interfere with the covers 21 a and cannot be assembled. Thus, incorrect assembly of the long storage-module busbars 33B and the short storage-module busbars 33A can be more reliably prevented.

As illustrated in FIGS. 9 and 10, a voltage sensor 35 is fixed with bolts 36 to a portion of the second connection plate 26B that faces two adjacent storage modules M. The voltage sensor 35 is shared by the two storage modules M, and is capable of detecting a voltage of the storage cells 11 included in each of the storage modules M by switching an electrical circuit included therein. Wires 37 that connect the storage cells 11 to the voltage sensor 35 extend from the storage-cell busbars 21. Since the storage-cell busbars 21 of the two storage modules M are disposed at both sides of the voltage sensor 35, the two wires 37 can be connected to the voltage sensor 35 without interfering with the voltage sensor 35. Accordingly, it is not necessary that the voltage sensor 35 be spaced from the second connection plate 26B to prevent the wires 37 from interfering with the voltage sensor 35. As a result, the size of the electric storage device P can be reduced.

Since the six storage modules M are electrically connected in series in the electric storage device P, the end plates 14A and 14B are alternately arranged on each of the first and second connection plates 26A and 26B (see FIGS. 5A, 5B, 6A, and 6B). In the case where the storage modules M are mounted in a vehicle in a horizontal orientation, the two fastening holes 23 d formed in each of the high-potential-side end plates 14A are arranged along a line that extends diagonally upward and leftward, and the two fastening holes 23 d formed in each of the low-potential-side end plates 14B are arranged along a line that extends diagonally upward and rightward. Accordingly, the reference fastening holes 26 a that are formed in the first and second connection plates 26A and 26B and that correspond to the fastening holes 23 d are also arranged along lines that extend diagonally upward and leftward or lines that extend diagonally upward and rightward. If the storage modules M are arranged such that the high-potential and low-potential sides thereof are reversed, the storage modules M cannot be attached to the first and second connection plates 26A and 26B, and incorrect assembly can thus be reliably prevented.

The end plates 14A and 14B having different shapes are formed by combining the main plates 22 and the sub-plates 23 having simple structures. Therefore, the number of types of components can be minimized and the cost can be reduced.

As illustrated in FIG. 11A, the electric storage device P is mounted in a vehicle such that the short storage-module busbars 33A face the front of the vehicle and the long storage-module busbars 33B face the rear of the vehicle. Wires 38 and 39 that extend from the storage-module terminals 31A at the front sides of the two storage modules M at the ends of the electric storage device P are connected t electronic devices including a contactor 40 and a fuse 41, respectively. Therefore, even when, for example, a rear collision of the vehicle occurs and a conductive component, such as a bumper beam, comes into contact with the electric storage device P, there are only two regions S in which short circuiting may occur. Since the pair of main terminals that have a largest potential difference therebetween in the electric storage device P are at a side closer to the front of the vehicle, short-circuiting of the main terminals can be prevented in case of a rear collision of the vehicle. In addition, since the wires 38 and 39 extend toward the contactor 40 and the fuse 41 from the front side of the electric storage device P, the lengths of the wires 38 and 39 can be minimized.

FIG. 11B illustrates an electric storage device P according to the related art in which six storage modules M are oriented in the same horizontal direction. If, for example, a rear collision of a vehicle occurs and a conductive component, such as a bumper beam, comes into contact with the electric storage device P, the number of regions S in which short circuiting may occur is three, which is greater than that in the present embodiment. In addition, since the pair of main terminals are at a side closer to the rear of the vehicle, there is a risk that short-circuiting of the main terminals will occur in case of a rear collision of the vehicle. In addition, wires 38 and 39 extend from a rear side of the electric storage device P to a contactor 40 and a fuse 41, respectively, and the lengths of the wires 38 and 39 are greater than those in the present embodiment.

As described above, according to the present embodiment, the risk that the storage-module terminals 31B of the electric storage device P will be short-circuited in case of a rear collision of the vehicle can be reduced. In addition, the lengths of the wires 38 and 39 which connect the electric storage device P to the contactor 40 and the fuse 41, respectively, can be reduced.

Although an embodiment of the present disclosure is described above, various design changes can be made within the scope of the present disclosure.

For example, the storage cells 11 according to the embodiment are not limited to lithium-ion batteries, and may instead be other types of batteries or capacitors.

In addition, although two types of busbars, which are the short storage-module busbars 33A and the long storage-module busbars 33B are used in the above-described embodiment, the number of types of busbars may instead be one.

In addition, although the contactor 40 is provided only at the positive-terminal side in the above-described embodiment, the contactor 40 may be provided not only at the positive-terminal side but also at the negative-terminal side. In this case, an additional contactor 40 may be disposed between the fuse 41 and the negative terminal in FIG. 11A.

In addition, although two short storage-module busbars 33A are provided in the above-described embodiment, one of them may be replaced by a service plug or a main switch for turning off the power supply for repair.

In addition, although the first and second storage modules M from each end in the arrangement direction are arranged such that the storage-cell busbars 21 thereof face away from each other in the above-described embodiment, they may instead be arranged such that the storage-cell busbars 21 thereof face each other. In this case, a surface of the third storage module M at a side opposite to the storage-cell-busbar-21 side faces a surface of the second storage module M at a side opposite to the storage-cell-busbar-21 side, and a surface of the third storage module M at the storage-cell-busbar-21 side faces a surface of the fourth storage module M at the storage-cell-busbar-21 side. In this case, the number of short storage-module busbars 33A is larger than the number of long storage-module busbars 33B, and the cost of the electric storage device P can be reduced as a result.

According to an aspect of the embodiment, the electric storage device includes a plurality of storage modules, each of which includes a plurality of storage cells that are electrically connected to each other with a storage-cell busbar. The storage-cell busbars of the storage modules have storage-module terminals at ends thereof, the storage-module terminals being electrically connected to each other with a storage-module busbar. The storage-module terminals are provided with stud bolts that are inserted through bolt holes formed in the storage-module busbar and nuts are fastened to the stud bolts.

Accordingly, the storage-module busbar can be fastened to the storage-module terminals without using bolts, so that switching of bolts can be prevented.

When the storage-module busbar according to the embodiment is assembled to the storage-module terminals, the stud bolts may extend in a direction that crosses the vertical direction.

In this case, when the stud bolts of the storage-module terminals are engaged with the bolt holes in the storage-module busbar, the nuts can be fastened to the stud bolts while the storage-module busbar is provisionally retained and prevented from falling due to gravity.

According to another aspect of the embodiment, an electric storage device includes a plurality of storage modules, each of which includes a plurality of storage cells that are electrically connected to each other with a storage-cell busbar. The storage modules are arranged next to each other and integrally fastened to a connection plate with first bolts. The storage-cell busbars of the storage modules have storage-module terminals at ends thereof, the storage-module terminals being electrically connected to each other with a storage-module busbar. The storage-module terminals are provided with stud bolts that extend in the same direction as an insertion direction of the first bolts, the stud bolts being inserted through bolt holes formed in the storage-module busbar and nuts are fastened to the stud bolts.

Accordingly, even when the insertion direction of the first bolts is the same as the direction in which the nuts are fastened, the first bolts and the nuts cannot be attached when they are switched. Therefore, switching between the first bolts and the nuts can be prevented.

A fastening distance of the stud bolts according to the embodiment may be smaller than a fastening distance of the first bolts.

In this case, according to the related art in which short bolts are used instead of the stud bolts, there is a risk that grounding will occur as a result of bolts longer than the bolts to be used being used by mistake. In contrast, according to the present disclosure, since the stud bolts are used, the risk that switching of the bolts will occur can be eliminated and the above-described problem can be solved.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 

What is claimed is:
 1. An electric storage device comprising: a plurality of storage modules each comprising: a storage-cell busbar including a first storage-module terminal at a first end of the storage-cell busbar; and a plurality of storage cells that are electrically connected to each other with the storage-cell busbar; and a first storage-module busbar with which the first storage-module terminal provided in one of the plurality of storage modules is electrically connected to the first storage-module terminal provided in another of the plurality of storage modules, the first storage-module terminal including a first stud bolt which extends through a bolt hole provided in the first storage-module busbar and to which a nut is fastened.
 2. The electric storage device according to claim 1, wherein, when the first storage-module busbar is assembled to the first storage-module terminal, the first stud bolt is disposed to extend in a direction that crosses a vertical direction.
 3. The electric storage device according to claim 1, wherein the storage-cell busbar includes a second storage-module terminal at a second end of the storage-cell busbar, and wherein the second storage-module terminal includes a second stud bolt to which a nut is fastened.
 4. The electric storage device according to claim 3, further comprising: a second storage-module busbar with which the second storage-module terminal provided in one of the plurality of storage modules is electrically connected to the second storage-module terminal provided in another of the plurality of storage modules, wherein the second stud bolt extends through a bolt hole provided in the second storage-module busbar.
 5. An electric storage device comprising: a plurality of storage modules each comprising: a storage-cell busbar including a first storage-module terminal at a first end of the storage-cell busbar; and a plurality of storage cells that are electrically connected to each other with the storage-cell busbar, the plurality of storage modules being arranged next to each other and integrally fastened to a first connection plate with first bolts; and a first storage-module busbar with which the first storage-module terminal provided in one of the plurality of storage modules is electrically connected to the first storage-module terminal provided in another of the plurality of storage modules, the first storage-module terminal including a first stud bolt which extends in a direction same as an insertion direction of the first bolts and to which a nut is fastened, the first stud bolt extending through a bolt hole provided in the first storage-module busbar.
 6. The electric storage device according to claim 5, wherein a fastening distance of the first stud bolt is smaller than a fastening distance of the first bolts.
 7. The electric storage device according to claim 6, wherein each of the plurality of storage modules comprises an end plate fastened to the plurality of storage cells, wherein the first connection plate is fastened to the end plate of each of the plurality of storage modules with the first bolts, wherein the fastening distance of the first stud bolt comprises a thickness of the first storage-module busbar, and wherein the fastening distance of the first bolts comprises a sum of a thickness of the first connection plate and a thickness of the end plate.
 8. The electric storage device according to claim 5, wherein the storage-cell busbar includes a second storage-module terminal at a second end of the storage-cell busbar, and wherein the second storage-module terminal includes a second stud bolt to which a nut is fastened.
 9. The electric storage device according to claim 8, further comprising: a second storage-module busbar with which the second storage-module terminal provided in one of the plurality of storage modules is electrically connected to the second storage-module terminal provided in another of the plurality of storage modules, wherein the plurality of storage modules are integrally fastened to a second connection plate with second bolts, wherein the second storage-module terminal extends in a direction same as an insertion direction of the second bolts, and wherein the second stud bolt extends through a bolt hole provided in the second storage-module busbar. 